diff --git a/build/mac/build_scripts/MozillaCheckoutList.txt b/build/mac/build_scripts/MozillaCheckoutList.txt
index 827937fe1e5..107f33f8370 100644
--- a/build/mac/build_scripts/MozillaCheckoutList.txt
+++ b/build/mac/build_scripts/MozillaCheckoutList.txt
@@ -7,7 +7,7 @@
 #   mozilla/gc, , 10/25/2000 12:00:00
 #
 
-mozilla/nsprpub,        NSPRPUB_CLIENT_TAG
+mozilla/nsprpub,        NSPRPUB_PRE_4_2_CLIENT_BRANCH
 mozilla/security/nss,   NSS_CLIENT_TAG
 mozilla/security/manager,
 mozilla/accessible,
diff --git a/client.mak b/client.mak
index 069b2ff97b4..3d4dfbf3d2c 100644
--- a/client.mak
+++ b/client.mak
@@ -113,7 +113,7 @@ NSPR_CO_FLAGS=$(MOZ_CO_FLAGS)
 !if "$(NSPR_CO_TAG)" != ""
 NSPR_CO_FLAGS=$(NSPR_CO_FLAGS) -r $(NSPR_CO_TAG)
 !else
-NSPR_CO_FLAGS=$(NSPR_CO_FLAGS) -r NSPRPUB_CLIENT_TAG
+NSPR_CO_FLAGS=$(NSPR_CO_FLAGS) -r NSPRPUB_PRE_4_2_CLIENT_BRANCH
 !endif
 
 CVSCO_NSPR = cvs $(CVS_FLAGS) co $(NSPR_CO_FLAGS)
diff --git a/client.mk b/client.mk
index 38ea0618f59..54c49613c91 100644
--- a/client.mk
+++ b/client.mk
@@ -53,7 +53,7 @@
 # For branches, uncomment the MOZ_CO_TAG line with the proper tag,
 # and commit this file on that tag.
 #MOZ_CO_TAG = <tag>
-NSPR_CO_TAG = NSPRPUB_CLIENT_TAG
+NSPR_CO_TAG = NSPRPUB_PRE_4_2_CLIENT_BRANCH
 PSM_CO_TAG = #We will now build PSM from the tip instead of a branch.
 NSS_CO_TAG = NSS_CLIENT_TAG
 LDAPCSDK_CO_TAG = LDAPCSDK_40_BRANCH